Harris ring

Last revised by Dr Daniel J Bell on 17 Apr 2022

A Harris ring is a ring-like shadow observed at the base of the odontoid process on a lateral radiograph of the cervical spine. It is formed by the superimposition of the lateral masses of the C2 vertebra (axis) on its body.

Disruption of the Harris ring is seen in type III, and less commonly, type II odontoid fractures.

In case of significant comminution of the C2 vertebral body, the anteroposterior diameter of the Harris ring may increase. It may be associated with an apparent increase in anteroposterior diameter of C2 vertebral body on lateral radiographs as compared to C3 vertebral body, and in this case is termed the “fat” C2 sign.

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Cases and figures

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